Method and apparatus for specimen fabrication

ABSTRACT

A sample fabricating method of irradiating a sample with a focused ion beam at an incident angle less than 90 degrees with respect to the surface of the sample, eliminating the peripheral area of a micro sample as a target, turning a specimen stage around a line segment perpendicular to the sample surface as a turn axis, irradiating the sample with the focused ion beam while the incident angle on the sample surface is fixed, and separating the micro sample or preparing the micro sample to be separated. A sample fabricating apparatus for forming a sample section in a sample held on a specimen stage by scanning and deflecting an ion beam, wherein an angle between an optical axis of the ion beam and the surface of the specimen stage is fixed and formation of a sample section is controlled by turning the specimen stage.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation application of U.S. application Ser.No. 10/898,592 filed on Jul. 26, 2004, now U.S. Pat. No. 7,268,356 whichis Continuation application of U.S. application Ser. No. 10/699,853filed on Nov. 4, 2003, now U.S. Pat. No. 6,794,663 which is aContinuation application of U.S. application Ser. No. 09/985,537 filedon Nov. 5, 2001 now U.S. Pat. No. 6,664,552. Priority is claimed basedon U.S. application Ser. No. 10/898,592 filed on Jul. 26, 2004, whichclaims the priority of U.S. application Ser. No. 10/699,853 filed onNov. 4, 2003, which claims the priority date of U.S. application Ser.No. 09/985,537 filed on Nov. 5, 2001, which claims the priority dates ofJapanese applications 2000-342372 and 2001-204768 filed on Nov. 6, 2000and Jul. 5, 2001, respectively, all of which is incorporated byreference.

BACKGROUND OF THE INVENTION

The present invention relates to method and apparatus specimenfabrication for analyzing, observing, or measuring a micro area byseparating a micro sample including a requested specific area from asample of an electronic part such as a semiconductor wafer or a deviceor preparing the micro sample to be separated by using a focused ionbeam.

Electronic parts such as a semiconductor memory typified by a dynamicrandom access memory, a microprocessor, a semiconductor device such as asemiconductor laser, and a magnetic head are required to be manufacturedin a high yield since decrease in the manufacturing yield due tooccurrence of a defect causes profit deterioration. Consequently, earlydetection/measure of/against a defect, a foreign matter, and poorprocessing as causes of a failure are big tasks. For example, at a siteof manufacturing a semiconductor device, energies are put into finding afailure by a careful test and analyzing the cause of the failure. In anactual electronic part manufacturing process using a wafer, a waferbeing processed is tested, the cause of an abnormal portion such as adefect in a circuit pattern or a foreign matter is tracked down, and ameasurement to be taken is examined.

Usually, to observe a fine structure of a sample, a scanning electronmicroscope (hereinbelow, abbreviated as SEM) with high resolution isused. However, as the packing density of a semiconductor device isbecoming higher, an object cannot be observed with the resolution of theSEM. Therefore, in place of the SEM, a transmission electron microscope(hereinbelow, abbreviated as TEM) having higher observation resolutionis used.

Conventional TEM sample fabrication is accompanied by a work of making asample into small pieces by cleaving, cutting, or the like. When thesample is a wafer, in most cases, the wafer has to be cut.

Recently, there is a micro area processing method of irradiating asample with an ion beam and applying an action that particlesconstructing the sample are released from the sample by sputtering, thatis, a method of using a process with a focused ion beam (hereinbelow,abbreviated as FIB). According to the method, first, a strip pellethaving a thickness of sub millimeters including an area to be observedis cut from a sample such as a wafer by using a dicer or the like. Apart of the strip pellet is processed with an FIB into a thin film stateto thereby prepare a TEM sample. The feature of the sample for TEMobservation processed with the FIB is that a part of a specimen isprocessed to a thin film having a thickness of about 100 nm for the TEMobservation. Although the method enables a requested observation area tobe positioned with accuracy of a micrometer level and to be observed,still, the wafer has to be cut.

Although monitoring a result of a process during fabrication of asemiconductor device or the like has an big advantage from the viewpointof managing the yield, a wafer is cut for preparation of a sample asdescribed above and a piece of the wafer is not subjected to a followingprocess but is discarded. In recent years, particularly, the diameter ofa wafer is increasing to reduce the price of manufacturing asemiconductor device. Specifically, the number of semiconductor deviceswhich can be manufactured from a single wafer is increased to reduce aunit price. However, it increases the price of the wafer itself, anadded value increases as the manufacturing process advances and,further, the number of semiconductor devices lost by discarding a waferincreases. Therefore, the conventional test method accompanying cuttingof the wafer is very uneconomical.

To deal with the problem, there is a method of preparing a samplewithout cutting a wafer. The method is disclosed in Japanese PatentApplication No. H05-52721, “Method of separating sample and method ofanalyzing sample separated by the separating method” (known technique1). According to the method, as shown in FIGS. 2( a) to 2(g), first, theposture of a sample 2 is maintained so that the surface of the sample 2is irradiated with an FIB 1 at the right angle and scanned with the FIB1 in a rectangular shape, and a rectangular hole 7 having a requireddepth is formed in the surface of the sample (FIG. 2( a)). Subsequently,the sample 2 is tilted and a bottom hole 8 is formed. The tilt angle ofthe sample 2 is changed by a specimen stage (not shown) (FIG. 2( b)).The posture of the sample 2 is changed, the sample 2 is disposed so thatthe surface of the sample 2 becomes perpendicular to the FIB 1 again,and a trench 9 is formed (FIG. 2( c)). By driving a manipulator (notshown), the tip of a probe 3 at the end of the manipulator is made comeinto contact with a portion to be separated in the sample 2 (FIG. 2(d)). A deposition gas 5 is supplied from a gas nozzle 10, and an areaincluding the tip of the probe 3 is locally irradiated with the FIB 1 toform an ion beam assist deposition film (hereinbelow, simply calleddeposition film 4). The separation portion in the sample 2 and the tipof the probe 3 which are in contact with each other are connected toeach other by the deposition film 4 (FIG. 2( e)). The peripheral portionis trenched with the FIB 1 (FIG. 2( f)), and a micro sample 6 as asample separated from the sample 2 is cut. The cut separated sample 6 issupported by the connected probe 3 (FIG. 2( g)). The micro sample 6 isprocessed with the FIB 1 and the area to be observed is walled, therebyobtaining a TEM sample (not shown). According to the method, a microsample including a requested analysis area is separated from a samplesuch as a wafer by using a process with an FIB and means for carryingthe micro sample. The micro sample separated by the method is introducedto any of various analyzers and can be analyzed.

A similar sample fabricating method is disclosed in Japanese PatentApplication Laid-Open No. H09-196213, “Apparatus and method forpreparing micro sample” (known technique 2). According to the method, asshown in FIGS. 9( a) to 9(j), first, the FIB 1 is emitted to form marks403 and 404 for identifying a target position and, after that,rectangular holes 401 and 402 are formed on both outer sides of themarks 403 and 404 in the sample 2 (FIG. 9( a)). Subsequently, a trench406 is formed with the FIB 1 (FIG. 9( b)). The specimen stage is tiltedand the surface of the sample is obliquely irradiated with the FIB 1,thereby forming a tapered trench 408, and an extraction sample 407 whichis connected to the sample 4 only via a residual area 405 is formed(FIG. 9( c)). The tilted specimen stage is returned to the originalposition and the probe 3 is controlled by a probe controller so as tocome into contact with a part of the extraction sample 407. The residualarea 405 of the extraction sample 407 will be cut with an FIB later. Inconsideration of a probe drift or the like, it is desirable to cut theresidual area 405 in short time, so that the volume of the residual area405 has to be low. Consequently, due to a fear that the residual area405 is destroyed by the contact of the probe 3, the probe 3 is madecontact while preventing a damage as much as possible by using the probecontrolling method. The probe 3 and the extraction sample 407 which arein contact with each other are fixed by using a deposition film 409(FIG. 9( d)). Subsequently, the residual area 405 is cut with the FIB 1(FIG. 9( e)). In such a manner, the extraction sample 407 is cut out,and the probe 3 is lifted by the probe driving apparatus to extract theextraction sample 407 (FIG. 9( f)). Subsequently, the cut extractionsample 407 is allowed to come into contact with a trench 411 formed inan extracted sample holder (FIG. 9( g)). At this time, the extractionsample 407 has to come into contact at a sufficiently low speed so thatthe extraction sample 407 is not destroyed or is not come off from theconnected portion with the deposition film 409, so that the contactingmethod is necessary. After making the extraction sample 407 contact withthe trench 411, they are fixed by using a deposition film 412 (FIG. 9(h)). After the fixing, the probe 3 connection portion is irradiated withthe FIB, and sputtering is performed to separate the probe from theextraction sample 407 (FIG. 9( i)). In the case of preparing a TEMsample, finally, the FIB 1 is emitted again to finish an observationarea 410 so that the thickness of the observation area 410 becomes about100 nm or less (FIG. 9( j)). In the case of preparing a sample foranalysis or measurement, the finishing process for making theobservation area thin (FIG. 9( j)) is not always necessary.

The example of employing the method of extracting a micro sample by thesample fabricating apparatus has been described above. There is also amethod of processing the shape of a micro sample by the samplefabricating apparatus, taking out the base from the sample fabricatingapparatus, and extracting the micro sample by another mechanism inatmosphere. For example, such a method is described by L. A. Giannuzziet al., “Focused Ion Beam Milling and Micromanipulation Lift-Out forSite Specific Cross-Section TEM Specimen Preparation”, Material ResearchSociety, Symposium Proceeding Vol. 480, pp. 19 to 27 (known technique3). Similarly, it is also descried by L. R. Herlinger, “TEM SamplePreparation Using a Focused Ion Beam and a Probe Manipulator”,Proceedings of the 22nd International Symposium for Testing and FailureAnalysis, pp. 199 to 205 (known technique 4).

According to such a method, as shown in FIG. 3( a), both sides of atarget position on a wafer 208 are processed in a stair shape with theFIB 1 to form a sample membrane 207, a specimen stage is tilted tochange the angle formed between the FIB 1 and the surface of the sample,and the sample is irradiated with the FIB 1. As shown in FIG. 3( b), theperiphery of the sample membrane 207 is cut with the FIB 1, therebyseparating the sample membrane 207 from the wafer. The wafer is takenout from an FIB system, a glass stick is allowed to approach the processportion in the atmosphere, the sample membrane 207 is attracted by theglass stick by using static electricity and is separated from the wafer,the glass stick is moved above a mesh 209 and is attracted by the mesh209 by using static electricity or disposed so that the process facefaces a transparent attachment. As described above, the processed microsample in the system may not be taken out in the system. Even when mostof the outer shape of the micro sample is processed with an ion beam,the separated micro sample is introduced into the TEM, and can beanalyzed.

By using any of the methods, without cutting a wafer, only a microsample or a membrane sample for test is extracted from a sample, and thewafer from which the sample is extracted can be returned to the nextprocess. Therefore, unlike the conventional techniques, there is nosemiconductor device which is lost by the cutting of a wafer, themanufacturing yield of the semiconductor device is increased in total,and the manufacturing cost can be reduced.

In the case of forming a hole by using sputtering of irradiating thesurface of a sample with an ion beam and observing a section of the holeby an FIB system or a scanning electron microscope (SEM), the section isformed at an end of an ion beam scan range.

However, the actually formed section is not perfectly perpendicular tothe surface of a sample due to flare of a processing beam andre-deposition of a sputtered substance, and a slight taper exists. AnFIB system having a mechanism of tilting a specimen stage can preventthe taper by tilting a sample by an angle corresponding to the taper,for example, about 0.5 degree and irradiating the tilted sample with anion beam and form an observation section having higher perpendicularity.The method is described as, for example, processing of a sample sectionof a transmission electron microscope (TEM), in “Electron and ion beamhandbook, Third Edition”, Japan Society for the Promotion of Science,132 commission, Nikkan Kogyo Shinbun Sha, pp. 459 and 460 (knowntechnique 5).

The conventional methods have the following problems. Specifically, toform the bottom hole 8 in the first known technique, to form the taperedtrench 408 in the second known technique, and to cut the periphery ofthe sample membrane 207 in the fourth known technique, the posture ortilt angle of the sample 2 is changed as a necessary process by thespecimen stage. However, as the diameter of a wafer increases, thespecimen stage also becomes larger. Consequently, a problem such that ittakes time to tile a large stage with high accuracy and, as a result,sample fabrication time becomes longer arises. Due to heavy weight ofthe specimen stage itself, the eucentric is not maintained before andafter the tilting and the sample position relative to the ion beamirradiating optical system moves, so that the focal point of the FIB isrelatively largely deviated from the surface of the sample, the surfaceof the sample cannot be observed, and a problem such that the ion beamirradiating optical system has to be re-adjusted also occurs. Thefunction of tilting the specimen stage causes increase in the size ofthe specimen stage itself and in the size of a specimen chamber forhousing the specimen stage. The trend of the diameter of a wafer isshifting from 200 mm to 300 mm. When the diameter of a wafer is furtherincreased to 400 mm, the size of the stage has to be increased and theproblem which occurs in association with the tilt of the specimen stagehas to be solved. In contrast, when the function of tilting the specimenstage of the system can be eliminated, miniaturization of the wholesystem can be realized and a problem such as a deviation of the sampleposition accompanying a tilt of the sample is solved. However, by theabove-described conventional methods, fabrication of a sample foranalyzing, observing or measuring a micro area by separating a microsample from an original sample (wafer) or preparing the micro sample tobe separated cannot be realized. Originally, the change in the tiltangle or posture of a sample is required due to existence of the fixedidea that the surface of a sample has to be irradiated with ion beams inat least two directions at different angles to separate a micro samplefrom an original sample or prepare the micro sample to be separated. Thetilting of the stage denotes here turning of a stage around a linesegment included in or parallel to the stage plane as an axis. It willbe simply described as tilting of a stage hereinlater.

By an FIB controller in which a specimen stage has the tilting function,an FIB can be emitted at an arbitrary angle, and can eliminate the taperas in the known technique 5.

On the other hand, the function of tilting a specimen stage can beomitted from the system, the miniaturization of the whole system isrealized, and the program such as a deviation of the sample positionwhich occurs in association with the tilting of a sample can be solved.However, according to the conventional methods, it is difficult to emitan FIB at an arbitrary angle. A method of obliquely irradiating thesurface of a sample with an ion beam to form a hole, thereby enabling anobservation section to be formed is disclosed as “Section observingmethod” in Japanese Patent Application Laid-Open No. H03-166744 (knowntechnique 6). Although a process of forming a vertical section by themethod is described, a method of optionally changing an irradiationangle without tilting a specimen stage is not mentioned. Consequently,it is difficult to eliminate the taper.

SUMMARY OF THE INVENTION

In consideration of the problems, a first object of the invention is toprovide a sample fabricating method for analyzing, observing, ormeasuring a micro area by separating a micro sample including arequested specific area from an original sample of an electronic partsuch as a semiconductor wafer, a semiconductor device, or the like orpreparing the micro sample to be separated without tilting a specimenstage by breaking down the conventional fixed idea. A second object isto provide a sample fabricating apparatus suitable for achieving thefirst object. A third object is to realize a sample fabricatingapparatus and a sample fabricating method which can form a section byirradiation with an FIB at an arbitrary angle in a certain range evenwhen a not-tilting specimen stage is used.

Terms used in the specification will be defined as follows.

A requested section is a section the operator of the apparatus intendsto prepare. A set section denotes a section obtained when it is assumedthat a set ion beam scanning area is ideally processed without aninfluence of a beam diameter, re-deposition, or the like. A formedsection is a section actually formed with an FIB. A formed-section edgeis a cross line between the formed section and the surface of a sample.A set-section edge is a cross line between the set section and thesurface of a sample. A scanning-area edge is one of the sides of an ionbean scanning area. A requested-section edge is a cross line of arequested section and the surface of a sample. A requested-section edgenormal direction is a direction of a normal line in a sample surface ofa requested section edge, which extends from the sample to a processspace. A requested section normal direction is a direction of a normalline of a requested section, which extends from the inside of the sampleto a process space. A requested depression angle is an angle formedbetween the requested-section normal direction and the sample surface.The requested depression angle is positive in the case where therequested-section normal line direction extends from the sample surfaceto the inside of the sample, and is negative in the case where therequested-section normal line direction extends from the inside of thesample to the surface of the sample (corresponding to an elevationangle). A set-section depression angle is an angle formed between theset-section normal line direction and the sample surface. Theset-section depression angle is positive when the set-section normalline direction extends from the sample surface to the inside of thesample and is negative when the set-section normal line directionextends from the inside of the sample to the surface of the sample(corresponding to an elevation angle).

The first object of the invention is achieved as follows.

Basic aspects of the invention to break down the conventional fixed ideathat the tilt angle or the posture of a sample has to be changed are asfollows.

(1) An ion beam processing method for separating a requested portion ina sample or preparing the requested portion by irradiating the samplewith an ion beam from a plurality of directions while fixing an angleformed between a sample placement face and an optical axis of an ionbeam to the sample.

According to the invention, the ion beam processing method foranalyzing, observing, or measuring a micro area by separating a microsample including a requested specific area from a sample of anelectronic part such as a semiconductor wafer, a semiconductor device,or the like or preparing the micro sample without tilting a specimenstage can be realized.

(2) A sample separating method for irradiating a sample with an ion beamwhile setting an angle formed between the optical axis of the ion beamemitted to the sample and the surface of the sample to be larger than 0degree and smaller than 90 degrees and irradiating a requested portionin the sample with the ion beam while fixing an angle formed between theoptical axis of the ion beam emitted to the sample and the samplesurface to thereby separate the requested portion or prepare therequested portion to be separated.

According to the invention, the sample fabricating method for analyzing,observing, or measuring a micro area by separating a micro sampleincluding a requested specific area from a sample of an electronic partsuch as a semiconductor wafer, a semiconductor device, or the like orpreparing the micro sample without tilting a specimen stage can berealized.

(3) A sample separating method for irradiating a sample with an ion beamwhile setting an angle formed between the optical axis of the ion beamemitted to the sample and the sample surface to be a range from 30degrees to 75 degrees, and irradiating a requested portion in the samplewith the ion beam while fixing the angle formed between the optical axisof the ion beam emitted to the sample and the sample surface, therebyseparating the requested portion or preparing the requested portion tobe separated.

According to the invention, the sample fabricating method for analyzing,observing, or measuring a micro area by separating a micro sampleincluding a requested specific area from a sample of an electronic partsuch as a semiconductor wafer, a semiconductor device, or the like orpreparing the micro sample without tilting a specimen stage can berealized. Particularly, by setting the FIB irradiation angle in therange from 30 degrees to 75 degrees, the surface of the sample can beobserved excellently, and the shape of the micro sample is formed to besuitable for fabrication.

(4) The object is also realized by a sample fabricating method forseparating a micro sample from a sample or preparing the micro sample tobe separated by using a sample fabricating apparatus including at leasta focused ion beam irradiating optical system, secondary particledetecting means for detecting secondary particles generated from asample irradiated with the focused ion beam, and a specimen stage onwhich a specimen base is placed, in which the sample is irradiated withthe focused ion beam by setting the angle formed between the opticalaxis of the focused ion beam emitted to the sample and the samplesurface to be larger than 0 degree and smaller than 90 degrees, and thesample is turned by using a sample surface normal line as a turning axisand is irradiated with the ion beam while fixing the angle formedbetween the optical axis of the focused on beam to the sample and thesample surface.

That is, an aspect of the invention for breaking down the conventionalfixed idea is to include an operation of turning a specimen stage aroundthe line normal to the sample surface as a turning axis into the samplefabricating method in accordance with an object. According to theinvention, the sample fabricating method for analyzing, observing, ormeasuring a micro area by separating a micro sample including arequested specific area from a sample of an electronic part such as asemiconductor wafer, a semiconductor device, or the like or preparingthe micro sample without tilting a specimen stage can be realized.

Also in the case of an apparatus in which the specimen stage has thetilting function, the time required to tilt the stage is unnecessary sothat the sample fabricating time is made relatively short. The problemsuch that the sample surface cannot be observed before and after thespecimen stage is tilted is also reduced.

(5) In the sample fabrication method of (4), the requested portion inthe sample is supported by a probe.

According to the invention, the sample fabricating method for analyzing,observing, or measuring a micro area by separating a micro sampleincluding a requested specific area from a sample of an electronic partsuch as a semiconductor wafer, a semiconductor device, or the like orpreparing the micro sample without tilting a specimen stage can berealized. By supporting the micro sample by the probe and extracting themicro sample from the specimen base, the section of the micro sample canbe observed in detail, and the position of processing the section can becontrolled with high precision. As the method of supporting the microsample, any method can be used as long as the micro sample can besupported such as fixing by using a deposition film, fixing by usingstatic electricity, or the like.

(6) A sample fabricating method for observation, analysis, ormeasurement, including: a step of forming a sample connected to aspecimen base via a residual area by a step of forming a rectangle holeby irradiating the sample with a focused ion beam while setting an angleformed between the optical axis of the focused ion beam emitted to thesample and the sample surface to be larger than 0 degree and smallerthan 90 degrees, a step of turning the sample by using a sample surfacenormal line as a turning axis, and a step of forming a tapered trench inthe surface of the specimen base by emitting a focused ion beam afterthe turn; a step of fixing the connected sample to a requested portionof transfer means by making a requested portion in the connected samplecontact with the requested portion of the transfer means, and forming adeposition film in an area including the contact portion by irradiatingthe area with a focused ion beam while supplying a deposition gas; and astep of cutting the residual area by emitting a focused ion beam.

According to the invention, the sample fabricating method for analyzing,observing, or measuring a micro area by separating a micro sampleincluding a requested specific area from a sample of an electronic partsuch as a semiconductor wafer, a semiconductor device, or the like orpreparing the micro sample without tilting a specimen stage can berealized. The section of the micro sample can be observed in detail, andthe section process position can be controlled with high precision.

(7) A sample fabricating method for observation, analysis, ormeasurement, including: a step of forming a membrane by forming arectangle hole by emitting a focused ion beam while setting an angleformed between the optical axis of the focused ion beam emitted to thesample and the sample surface to be larger than 0 degree and smallerthan 90 degrees; a step of turning the sample by using a sample surfacenormal line as a turning axis, and a step of separating the samplemembrane or preparing the sample membrane to be separated by emitting afocused ion beam after the turn.

According to the invention, the sample fabricating method for analyzing,observing, or measuring a micro area by separating a micro sampleincluding a requested specific area from a sample of an electronic partsuch as a semiconductor wafer, a semiconductor device, or the like orpreparing the micro sample without tilting a specimen stage can berealized. Since a process of forming an ion beam assist deposition filmor the like is not included, the sample fabrication time can beshortened.

(8) In the sample fabricating method in any of (3), (4), (5), (6), and(7), in order to separate at least two micro samples or prepare themicro samples to be separated, the peripheral area of each of microsamples is processed to some midpoint of all the processes, the sampleis turned, and the process of the peripheral area of each of the microsamples is sequentially continued.

According to the invention, the sample fabricating method for analyzing,observing, or measuring a micro area by separating a micro sampleincluding a requested specific area from a sample of an electronic partsuch as a semiconductor wafer, a semiconductor device, or the like orpreparing the micro sample without tilting a specimen stage can berealized. Particularly, a plurality of samples can be prepared with highthroughput.

The second object of the invention is achieved as follows.

(9) A sample fabricating apparatus including at least a focused ion beamirradiating optical system and a specimen stage on which a specimen baseis placed, for separating a micro sample from the specimen base orpreparing the micro sample to be separated, wherein an angle formedbetween an almost center axis of a mechanical column including thefocused ion beam irradiating optical system and the sample placementface of the specimen stage is fixed, and the apparatus has a separatorfor separating a desired portion in the sample and a probe forsupporting the separated sample.

According to the invention, the sample fabricating method for analyzing,observing, or measuring a micro area by separating a micro sampleincluding a requested specific area from a sample of an electronic partsuch as a semiconductor wafer, a semiconductor device, or the like orpreparing the micro sample without tilting a specimen stage can berealized. By supporting the micro sample by the probe and extracting themicro sample from the specimen base, the section of the micro sample canbe observed in detail, and the sample fabricating apparatus capable ofcontrolling the section process position with high precision can berealized. As the method of supporting the micro sample, any method canbe used as long as the micro sample can be supported such as fixing byusing a deposition film, fixing by using static electricity, or thelike.

(10) A sample fabricating apparatus for separating a micro sample from aspecimen base or preparing the micro sample to be separated, includingat least a focused ion beam irradiating optical system, secondaryparticle detecting means for detecting secondary particles generatedfrom a sample irradiated with the focused ion beam, and a specimen stageon which a specimen base is placed, wherein the angle formed between theoptical axis of the focused ion beam emitted to the sample and thesample surface is larger than 0 degree and smaller than 90 degrees, thespecimen stage has the function of turning around a sample surfacenormal line as a turn axis, and the apparatus has the function ofdetermining, after the turn, the position irradiated with the focusedion beam for separating a sample or preparing the sample to be separatedby using image displaying means for displaying a secondary particleimage formed by secondary particles generated from the sample irradiatedwith the focused ion beam or an electron beam emitted from an electronbeam emitting system separately provided.

According to the invention, the sample fabricating apparatus forpreparing a sample for analyzing, observing, or measuring a micro areaby separating a micro sample including a requested specific area from asample of an electronic part such as a semiconductor wafer, asemiconductor device, or the like or preparing the micro sample to beseparated without tilting the specimen stage, which is suitable from theviewpoints that operations of the apparatus can be automated and theburden on the operator can be lessened and can prepare a sample in whicha damage in the sample surface is little in a short time can berealized.

(11) A sample fabricating apparatus for separating a micro sample from aspecimen base or preparing the micro sample to be separated, includingat least a focused ion beam irradiating optical system, secondaryparticle detecting means for detecting secondary particles generatedfrom a sample irradiated with the focused ion beam, and a specimen stageon which a specimen base is placed, wherein the angle formed between theoptical axis of the focused ion beam emitted to the sample and thesample surface is larger than 0 degree and smaller than 90 degrees, thespecimen stage has the function of turning around a sample surfacenormal line as a turn axis, and the apparatus has the function ofdetermining, after the turn, the position irradiated with the focusedion beam for separating a sample or preparing the sample to be separatedby using a result of performing an image process on a secondary particleimage formed by secondary particles generated from the sample irradiatedwith the focused ion beam or an electron beam emitted from an electronbeam emitting system separately provided.

According to the invention, the sample fabricating apparatus forpreparing a sample for analyzing, observing, or measuring a micro areaby separating a micro sample including a requested specific area from asample of an electronic part such as a semiconductor wafer, asemiconductor device, or the like or preparing the micro sample to beseparated without tilting the specimen stage, which is suitable from theviewpoints that operations of the apparatus can be automated and theburden on the operator can be lessened and can prepare a sample in whicha damage in the sample surface is little in a short time can berealized.

(12) A sample fabricating apparatus for separating a micro sample from aspecimen base or preparing the micro sample to be separated, includingat least a focused ion beam irradiating optical system, secondaryparticle detecting means for detecting secondary particles generatedfrom a sample irradiated with the focused ion beam, and a specimen stageon which a specimen base is placed, wherein the angle formed between thefocused ion beam irradiating optical system and the sample surface is ina range from 30 degrees to 75 degrees, the specimen stage has a turningfunction around a normal line to the sample surface as a rotation axis,and the apparatus includes a transfer means for transferring anextracted micro sample which is a desired portion separated from thespecimen base to another member, and a holding means of a sample holderon which the extracted micro sample is placed.

The sample fabricating apparatus is suitable for fabricating a samplefor analyzing, observing, and measuring a micro area by separating amicro sample including a requested specific area from a sample of anelectronic part such as a semiconductor wafer, a semiconductor device,or the like or preparing the micro sample to be separated withouttilting the specimen stage. Particularly, by irradiating the focused ionbeam at an angle from 30 degrees to 75 degrees, the surface of thesample can be observed excellently, and the shape of the micro sample issuitable for easy fabrication. The sample fabricating apparatus capableof fabricating a sample in shorter time can be realized.

(13) A sample fabricating apparatus for separating a micro sample from aspecimen base or preparing the micro sample to be separated, includingat least a focused ion beam irradiating optical system, secondaryparticle detecting means for detecting secondary particles generatedfrom a sample irradiated with the focused ion beam, and a specimen stageon which a specimen base is placed, in which the angle formed betweenthe optical axis of the focused ion beam emitted to the sample and thesample surface is 45 degrees, the specimen stage has a function ofturning around a sample surface normal line as a rotation axis, and theapparatus includes a transfer means for transferring an extracted microsample which is a requested portion separated from the specimen base toanother member, and a holding means of a sample holder on which theextracted micro sample is placed.

According to the invention, the sample fabricating apparatus forpreparing a sample for analyzing, observing, or measuring a micro areaby separating a micro sample including a requested specific area from asample of an electronic part such as a semiconductor wafer, asemiconductor device, or the like or by preparing the micro sample to beseparated without tilting the specimen stage can be realized. Theapparatus is suitable for separating a sample or preparing the sample tobe separated since the angle of the focused ion beam can be set to 45degrees in both of the cases of observing the sample surface and asection of the sample by irradiation with the focused ion beam under thesame conditions. Further, the sample fabricating apparatus capable ofpreparing a sample having little damage in its surface in a short timecan be realized.

(14) In the sample fabricating apparatus in any of (10), (11) (12), and(13), the optical axis of the focused ion beam emitted to the samplealmost coincides with the mechanical center axis of an objective lensalmost symmetrical with respect to the center as a component of thefocused ion beam irradiating optical system.

According to the invention, the sample fabricating apparatus capable offabricating a sample for analyzing, observing, or measuring a micro areaby separating a micro sample including a requested specific area from asample of an electronic part such as a semiconductor wafer, asemiconductor device, or the like or preparing the micro sample to beseparated without tilting the specimen stage can be realized bymechanically specifying the angle formed between the objective lensalmost symmetrical with respect to the center as a component of thefocused ion beam irradiating optical system and the surface of thespecimen stage, so that designing of the apparatus can be simplified.

(15) A sample fabricating apparatus including at least a focused ionbeam irradiating optical system, secondary particle detecting means fordetecting secondary particles generated from a sample irradiated withthe focused ion beam, and a specimen stage on which a specimen base isplaced, in order to separate a micro sample from the specimen base orpreparing the micro sample to be separated, for irradiating a peripheralarea of the micro sample in the specimen stage with the focused ion beamfrom a plurality of incident directions to thereby separate the microsample or prepare the micro sample to be separated, in which the focusedion beam irradiating optical system is provided with a focused ion beamtilting function of changing the optical axis of the focused ion beamemitted to the sample by at least 15 degrees.

According to the invention, the sample fabricating apparatus capable offabricating a sample for analyzing, observing, or measuring a micro areaby separating a micro sample including a requested specific area from asample of an electronic part such as a semiconductor wafer, asemiconductor device, or the like or preparing the micro sample to beseparated without tilting the specimen stage can be realized by thefocused ion beam tilting function capable of changing the incidentdirection of the focused ion beam at least by 15 degrees. Particularly,the focused ion beam incident angle can be selected in preparation of asample, so that various sample fabricating methods and various sampleshapes can be realized.

(16) In the sample fabricating apparatus of (15), the focused ion beamtilting function capable of changing the optical axis of the focused ionbeam emitted to the sample by at least 15 degrees is realized by amechanism of varying the tilt angle with respect to the specimen stageof a mechanical column including the focused ion beam irradiatingoptical system.

According to the invention, the sample fabricating apparatus capable offabricating a sample for analyzing, observing, or measuring a micro areaby separating a micro sample including a requested specific area from asample of an electronic part such as a semiconductor wafer, asemiconductor device, or the like or preparing the micro sample to beseparated without tilting the specimen stage can be realized by themechanism of varying the tilt angle with respect to the specimen stageof the mechanical column including the focused ion beam irradiatingoptical system. Particularly, the focused ion beam incident angle can beselected in preparation of a sample, so that various sample fabricatingmethods and various sample shapes can be realized.

(17) In the sample fabricating apparatus of (15), the focused ion beamtilting function capable of changing the optical axis of the focused ionbeam emitted to the sample by at least 15 degrees is realized by anelectric deflecting mechanism.

According to the invention, the sample fabricating apparatus capable offabricating a sample for analyzing, observing, or measuring a micro areaby separating a micro sample including a requested specific area from asample of an electronic part such as a semiconductor wafer, asemiconductor device, or the like or preparing the micro sample to beseparated without tilting the specimen stage can be realized by theelectric deflecting mechanism. Particularly, the mechanical apparatusconfiguration is simplified, the manufacturing cost can be reduced, andthe focused ion beam incident angle can be selected in preparation of asample, so that various sample fabricating methods and various sampleshapes can be realized.

(18) In the sample fabricating apparatus in any of (10), (11) (12),(13), (14), (15), (16), and (17), the specimen stage has a fixed tiltangle using a line segment included in the stage plane or a line segmentparallel to the stage plane as a tilt axis.

According to the invention, since the specimen stage does not have thetilting function, miniaturization of the whole apparatus can berealized, and the sample fabricating apparatus capable of fabricating asample for analyzing, observing, and measuring a micro area byseparating a micro sample including a requested specific area from asample of an electronic part such as a semiconductor wafer, asemiconductor device, or the like or preparing the micro sample to beseparated can be realized.

(19) In the sample fabricating apparatus in any of (9), (10), (11),(12), (13), (14), (15), (16), and (17), the specimen stage isconstructed by combining a stage which is turned at a specific fixedangle and a stage which can be turned at an arbitrary angle.

According to the invention, since the specimen stage does not have thetilting function, miniaturization of the whole apparatus can berealized, and the sample fabricating apparatus capable of fabricating asample for analyzing, observing, and measuring a micro area byseparating a micro sample including a requested specific area from asample of an electronic part such as a semiconductor wafer, asemiconductor device, or the like or preparing the micro sample to beseparated can be realized. Particularly, the apparatus is suitable forsaving the time necessary for positioning and increasing the throughputof sample preparation.

(20) In the sample fabricating apparatus in any of (9), (10) (11), (12),(13), (14), (15), (16), and (17), the specimen stage is constructed bycombining a stage which is turned at a fixed angle that is at least oneof 90 degrees and 180 degrees and a stage which can be turned at anarbitrary angle.

According to the invention, since the specimen stage does not have thetilting function, miniaturization of the whole apparatus can berealized, and the sample fabricating apparatus capable of fabricating asample for analyzing, observing, and measuring a micro area byseparating a micro sample including a requested specific area from asample of an electronic part such as a semiconductor wafer, asemiconductor device, or the like or preparing the micro sample to beseparated can be realized. Particularly, the apparatus is suitable forsaving the time necessary for positioning and increasing the throughputof sample preparation.

The third object of the invention is achieved by the following.

(21) A sample fabricating apparatus for forming a sample section in asample by ion beam processing, including an ion beam optical systemconstructed by an ion source, a lens for condensing ions emitted fromthe ion source, and a deflector, an ion beam optical system controllerfor controlling the ion beam optical system, a detector for detectingsecondary particles generated from a sample irradiated with an ion beam,a specimen stage for holding the sample, and a specimen-stage positioncontroller for controlling the position of the specimen stage, in whichan angle formed between the optical axis of the ion beam emitted fromthe ion beam optical system and the sample surface is fixed andformation of a sample section is controlled in correspondence with aset-section depression angle. Thus, also in the apparatus in which thetilting of the specimen stage with respect to the ion beam opticalsystem cannot be changed, a section at an arbitrary tilt angle can beformed.

(22) A sample fabricating apparatus for forming a sample section in asample by ion beam processing, including an ion beam optical systemconstructed by an ion source, a lens for condensing ions emitted fromthe ion source, and a deflector, an ion beam optical system controllerfor controlling the ion beam optical system, a detector for detectingsecondary particles generated from a sample irradiated with an ion beam,a specimen stage for holding the sample, and a specimen-stage positioncontroller for controlling the position of the specimen stage, in whichthe ion beam optical system controller has a construction that an angleformed between the optical axis of the ion beam emitted from the ionbeam optical system and the sample surface is larger than 0 degree andsmaller than 90 degrees, and controls an ion beam scan by the deflectorin correspondence with a set-section depression angle of a set section.Thus, the FIB irradiating angle at the time of processing a section canbe arbitrarily set.

(23) In the sample fabricating apparatus in each of (21) and (22), theion beam optical system controller controls the deflector on the basisof angle information that a requested depression angle is projected to aplane including, as a normal line, the optical axis of the ion beam incorrespondence with a set-section depression angle of a set section.Thus, the ion beam processing set angle is controlled and the FIBirradiating angle at the time of processing a section can be arbitrarilyset.

(24) In the sample fabricating apparatus in each of (21) and (22), theion beam optical system controller controls the deflector on the basisof angle information that a set-section depression angle is projected toa plane including, as a normal line, the optical axis of the ion beam incorrespondence with a set-section depression angle of a set section, andthe specimen-stage position controller controls turning in the specimenstage plane of the specimen stage. Thus, a section at an arbitrarydepression angle can be easily formed in an arbitrary processingposition by turning a sample.

(25) In the sample fabricating apparatus in any of (21) to (24), angleinformation that a set-section depression angle of a set section isprojected to a plane including, as a normal line, the optical axis ofthe ion beam is displayed on a display for displaying secondary particleinformation detected by the secondary particle detector and is set. Withthe configuration, the operator can visually make processing settingcorresponding to a requested FIB irradiating angle.

(26) In the sample fabricating apparatus in each of (21) and (22), incorrespondence with parameters of coordinates of a requested-sectionedge, a requested-section normal line direction, and a size, parametersequivalent to the parameters, or a combination of those parameters, theion beam optical system controller controls the ion beam deflector, andthe specimen-stage position controller controls turn in the specimenstage plane of the specimen stage. With the configuration, processingsetting corresponding to section forming parameters desired by theoperator can be automated.

(27) In the sample fabricating apparatus in any of (21) to (26), aninput apparatus for setting a requested-section depression angle of arequested section or a parameter equivalent to the requested-sectiondepression angle is provided. With the configuration, the operator caneasily set the depression angle of the requested section.

(28) A sample fabricating method for irradiating a sample with an ionbeam from an oblique direction to prepare a section by sputtering,including a step of setting a depression angle of a section requested tobe observed in a sample, a step of determining a scanning-area edge ofan ion beam in corresponding to the depression angle and setting ascanning area, and a step of processing the scanning area with the ionbeam. Only by deflecting the ion beam, a section at an arbitrary tiltangle in a certain range can be formed.

(29) In the sample fabricating method of (28), by preparing a samplefrom a step of obtaining a turn angle of the requested section and astep of determining a turn angle of the sample in correspondence withthe depression angle and the turn angle of the requested section, andsetting turn in the specimen stage plane of the specimen stage, asection at an arbitrary tilt angle in a certain range in the requestedsection position can be formed.

(30) In a sample fabricating apparatus for forming a sample section in asample held on a specimen stage by processing with a charged particlebeam by using a charged particle beam optical system for condensing,scanning and deflecting a charged particle beam emitted from a chargedparticle source, an angle formed between the optical axis of the chargedparticle beam emitted from the charged particle beam optical system anda surface of the specimen stage is fixed, and formation of a samplesection is controlled by turning of the specimen stage in the specimenstage plane.

(31) In a sample fabricating apparatus for forming a sample section in asample held on a specimen stage by processing with a charged particlebeam by using a charged particle beam optical system for condensing,scanning and deflecting a charged particle beam emitted from a chargedparticle source, an angle formed between the optical axis of the chargedparticle beam emitted from the charged particle beam optical system anda surface of the sample is fixed, and the scanning and deflection of thecharged particle beam optical system is controlled in correspondencewith an angle formed between a direction of a normal line of a sectionwhich is set for forming a sample section requested to be observed inthe sample and the surface of the sample.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1( a) to 1(f) are diagrams for explaining an embodiment of asample fabrication method according to the invention.

FIGS. 2( a) to 2(g) are diagrams for explaining a conventional method ofpreparing a TEM sample and, particularly, an example of using an FIB andcarrying means.

FIGS. 3( a) and 3(b) are diagrams for explaining the conventional methodof preparing a TEM sample and, particularly, an example of separating athin film from a specimen base with an FIB.

FIG. 4 is a configuration block diagram showing an embodiment of asample fabricating apparatus according to the invention.

FIGS. 5( a) and 5(b) are diagrams of micro samples prepared by thesample fabricating method according to the invention.

FIGS. 6( a) to 6(d) are diagrams for explaining an embodiment of thesample fabricating method according to the invention.

FIG. 7 is a configuration block diagram showing an embodiment of asample fabricating apparatus according to the invention.

FIGS. 8( a) and 8(b) are supplementary diagrams for understanding ofFIGS. 1( a) to 1(f).

FIGS. 9( a) to 9(j) are diagrams for explaining a conventional TEMsample fabricating method and, particularly, an example using an FIB andcarrying means.

FIGS. 10( a) and 10(b) are configuration block diagrams each showing anembodiment of a sample fabricating apparatus according to the invention.

FIG. 11 is a configuration block diagram showing an embodiment of asample fabricating apparatus according to the invention.

FIGS. 12( a) to 12(d) are diagrams for explaining a sample preparingprocedure of the embodiment.

FIG. 13 is a general configuration diagram showing an embodiment of asample fabricating apparatus according to the invention.

FIG. 14 is a diagram showing an example of forming a section with an ionbeam emitted in an oblique direction.

FIG. 15 is a diagram showing a section process setting screen on asecondary electron image.

FIG. 16 is a diagram showing a section formed by emitting a parallel ionbeam with respect to a requested section.

FIG. 17 is a diagram showing a section formed by emitting a tilted ionbeam with respect to a requested section.

FIGS. 18( a) and 18(b) are diagrams each showing a section processsetting screen on a secondary electron image at the time of irradiatinga tilted ion beam.

FIG. 19 is a diagram showing a section formed with a tilted ion beam.

FIGS. 20( a) and 20(b) are diagrams each showing turning of a sample tomake a structure in which a section is formed coincide with processsetting.

FIG. 21 is a flow chart of process setting in the invention.

FIGS. 22( a) and 22(b) are diagrams each showing a process settingscreen.

FIG. 23 is a diagram showing a membrane forming process by parallelirradiation of an ion beam for a requested section.

FIGS. 24( a) and 24(b) are diagrams each showing a membrane formingprocess with a tilted ion beam for a requested section.

FIGS. 25( a) and 25(b) are diagrams each showing a process for forming asample section adapted to analyze composition in the depth direction.

FIG. 26 is a diagram showing the relation between a depression angle ofa set section and a depression angle of a formed section by experiments.

FIGS. 27( a) and 27(b) are diagrams showing a difference between devicepattern processes according to sample surface process shapes.

FIG. 28 is a diagram showing a scanning area for forming a rectangularhole.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of a sample fabricating apparatus according to theinvention includes at least: a focused ion beam irradiating opticalsystem disposed so that a focused ion beam is emitted at an angle formedbetween the surface of a sample on a stage and the optical axis of afocused ion beam, larger than 0 degree and smaller than 90 degrees;secondary electron detecting means for detecting secondary electronsgenerated from the sample irradiated with the focused ion beam; and aspecimen stage of a structure having no tilting mechanism.

Concrete embodiments will be described hereinbelow.

First Embodiment

A schematic configuration of a sample fabricating apparatus as anembodiment of the invention will be describe by referring to FIG. 4.

A sample fabricating apparatus 17 has a vacuum chamber 41 in which anion beam irradiating optical system 35 constructed by an ion source 32,a beam limiting aperture 33, an ion beam scanning electrode 34, an ionbeam lens 31, and the like; a secondary electron detector 36 fordetecting secondary electrons and secondary ions emitted from a sampleirradiated with an FIB; a deposition-gas supplying source 37 forsupplying an original material gas to form a deposition film in an ionbeam irradiation area; the probe 3 attached at the tip of a manipulator42; a specimen stage 39 on which a specimen base 38 such as asemiconductor wafer or a semiconductor chip is placed; a sample holder40 for fixing a micro sample as a part extracted from the specimen base38, and the like are disposed. In this case, the ion beam irradiatingoptical system 35 is mounted relative to the stage 39 so that the angleformed by an almost center axis of an objective lens 44 and the surfaceof the sample becomes almost 45 degrees. The specimen stage 39 has thefunction of turning around a line segment perpendicular to the surfaceof a sample as a rotation axis. As apparatuses for controlling theapparatus, a stage controller 61 mainly including an electric circuitand an arithmetic unit, a manipulator driver 62, an amplifier 63 for thesecondary electron detector, a deposition gas controller 64, an FIBcontroller 65, a central processing unit 74, and the like are disposed.The central processing unit 74 has the function of recognizing the shapeof a sample by performing an image process on a secondary electron imageformed by secondary electrons generated from the sample irradiated withthe FIB. The central processing unit 74 also has the function ofirradiating a desired position in the sample shape with the FIB 1 by theFIB controller 65 on the basis of sample shape information.

An operation of the sample fabricating apparatus will now be described.First, ions released from the ion source 32 are emitted to the specimenbase 38 via the beam limiting aperture 33, ion beam lens 31, andobjective lens 44. The FIB 1 is narrowed so that its diameter becomes afew nm to about 1 micrometer on the sample. When the specimen base 38 isirradiated with the FIB 1, atoms constructing the surface of the sampleare released to the vacuum by a sputtering phenomenon. By making a scanwith the FIB 1 by using the ion beam scanning electrode 34, processingat a micrometer level to a sub-micrometer level can be performed. Byirradiating the specimen base 38 with the FIB 1 while introducing adeposition gas into the specimen chamber, a deposition film can beformed. In such a manner, the specimen base 38 can be processed byskillfully using the sputtering or deposition with the FIB 1. Thedeposition film formed by the irradiation with the FIB 1 is used toconnect the contact portion at the tip of the probe 3 and the sample orto fix the extracted sample to a sample holder 40. A scan with the FIB 1is performed, secondary electrons and secondary ions emitted from thesample are detected by the secondary electron detector 36, and theintensities of the detected secondary electrons and secondary ions areconverted to the luminance of an image, thereby enabling the specimenbase 38, the probe 3, and the like to be observed.

A sample fabricating method as an embodiment of the invention will nowbe described by referring to FIGS. 1( a) to 1(f). To understand FIGS. 1(a) to 1(f), as a supplement, refer to FIG. 8A showing a rectangular hole501 fabricated when the FIB irradiation axis is normal to the surface ofa sample and FIG. 8B showing a rectangular hole 502 fabricated when theFIB irradiation axis is at 45 degrees from the surface of a sample.

A sample is prepared as follows. First, a mark indicative of thefabrication position of a membrane for TEM observation and a protectionfilm are formed on the base. Subsequently, a rectangle whose one side isin the direction of projection of the optical axis of an FIB to the basesurface onto the surface of the sample is scanned with the FIB 1 on thespecimen base to thereby form two rectangular holes 101 (FIG. 1( a))having a depth of about 15 .mu.m and tapered in the depth direction anda trench 102 similarly tapered in the depth direction (FIG. 1( b)). TheFIB optical axis is tilted by 45 degrees from the surface of the sample.Subsequently, by using the axis perpendicular to the surface of thesample as a rotation axis, the sample is turned by about 180 degrees. Byperforming an image process on a secondary electron image formed bysecondary electrons generated from the sample irradiated with the FIB 1,the two rectangular holes and the trench formed so far are recognized.The FIB irradiation position is controlled by the FIB controller 65 onthe basis of the sample shape information, and a trench 103 similarlytapered in the depth direction is formed (FIG. 1( c)). Subsequently, bydriving the probe controller, the tip of the probe 3 is made come intocontact with the micro sample 6 on the base. After that, a depositiongas is supplied from the gas nozzle, an area including the tip portionof the probe 3 is locally irradiated with the FIB 1, and a depositionfilm 105 is formed to connect the portion separated from the base andthe probe 3 which are in contact (FIG. 1( d)). By cutting a residualarea 104 with the FIB 1, the micro sample 6 enters a state supported bythe probe 3 connected (FIG. 1( e)). By moving the probe 3 upward, themicro sample 6 can be extracted (FIG. 1( f)). The following processesare similar to those in the conventional technique. Specifically, thespecimen stage is operated while the probe is stopped above the specimensurface, thereby moving the micro sample onto a sample mesh. The microsample is fixed to the sample mesh by using a deposition film. The probeis cut with the FIB so as to be separated from the micro sample.Finally, the observation area in the micro sample is thinned to athickness of about 100 nm with the FIB, thereby completing the TEMsample.

In the method, to form the trench tapered in the depth direction in FIG.1( c), the sample is turned by about 180 degrees. Alternately, thetrench may be also formed by turning the sample by about 90 degrees byusing the axis perpendicular to the surface of the sample as a rotationaxis. The shape of the micro sample in this case is as shown in FIG. 5(a). The shape of the micro sample formed by turning the sample by about180 degrees is as shown in FIG. 5( b). The order of formation of the tworectangular holes (FIG. 1( a)), the trench (FIG. 1( b)) similarlytapered in the depth direction, and the trench (FIG. 1( c)) formed byturning the sample by about 180 degrees or 90 degrees is not limited.

In the embodiment, by performing image processing on a secondaryelectron image formed by secondary electrons generated from the sampleirradiated with the FIB, the two rectangular holes and the trenchesformed so far are recognized and the FIB irradiation position iscontrolled by the FIB controller on the basis of the sample shapeinformation. The operation can be therefore automated and the burden onthe operator can be lessened. However, it is not always necessary to usean image processor. The operator of the apparatus can control the FIBirradiation position by observing a secondary electron image on an imagedisplay.

In the case of forming a plurality of micro samples, each of the samplescan be fabricated in accordance with the order. First, two rectangularholes 101 (FIG. 1( a)) having a depth of about 15 .mu.m and tapered inthe depth direction and the trench 102 (FIG. 1( b)) similarly tapered inthe depth direction are formed in necessary positions in each of aplurality necessary number of samples. By using an axis perpendicular tothe surface of the sample as a rotation axis, the sample is turned byabout 180 degrees. Subsequently to the positioning of the samples, thetrench 103 tapered in the depth direction is formed in each of thesamples (FIG. 1( c)). The probe controller is driven to fabricate aplurality of micro samples 6 as TEM samples in accordance with the orderby using the probe 3. In such a manner, the turning operation requiringrelatively long time can be reduced. Thus, a plurality of samples can befabricated with throughput higher than that in the case of fabricatingeach of the samples in accordance with the order.

In the foregoing embodiment, in the series of processes of separatingthe micro sample from the specimen base, the angle formed between theFIB and the sample surface is 45 degrees and unchanged. That is, theprocess of tilting the stage is not included. According to theembodiment, therefore, even when the function of tilting the specimenstage is omitted to reduce the size of the whole apparatus, preparationof a sample for analyzing, observing, or measuring a micro area byseparating a micro sample from a sample or preparing the micro sample tobe separated can be realized. Also in the case of the apparatus in whichthe specimen stage has the tilting function different from theembodiment, the invention is valid. The time required to tilt the stageis unnecessary, so that the sample preparation time becomes relativelyshorter. A problem such that the surface of the sample cannot beobserved before and after the specimen stage is tilted is reduced. Inthe embodiment, a micro sample is extracted from the specimen base atthe time of forming a membrane for the TEM sample, so that the sectionof the micro sample can be observed in detail, and the sectionprocessing position can be controlled with high precision.

According to the embodiment, the sample fabricating apparatus forpreparing a sample for analyzing, observing, or measuring a micro areaby separating a micro sample from a sample or preparing the micro sampleto be separated, which is suitable from the viewpoints that operationsof the apparatus can be automated and the burden on the operator can belessened is provided.

In the embodiment, the specimen stage is constructed by combining astage which turns at a predetermined fixed angle and a stage which canbe turned at an arbitrary angle. The stage which is turned at the fixedangle is turned by 180 degrees or 90 degrees as described above. Thestage which is turned at an arbitrary angle is operated by adjusting aprocessing position on a sample or the like. Generally, the precisionfor determining the turn angle of the stage which turns at an arbitraryangle is at most 0.01 degree. As in the embodiment, in the case wherefine positioning is necessary after the turn, precision is insufficient.However, in the stage having the function of only the turning at aspecified fixed angle, the turn precision can be further increased.Therefore, the operation for turning the stage by a fixed angle toadjust the process position after the turn of 180 degrees or 90 degreesin the embodiment is suitable to shorten the time required for thepositioning and to increase the throughput of preparing the sample.

In the embodiment, the FIB optical axis is set to 45 degrees from thesurface of a sample. In the case of observing both the surface of asample and a sample section by the irradiation with an FIB, the FIBirradiation angle is 45 degrees in both cases, and both of them can beobserved under similar conditions. Thus, 45 degrees is suitable forseparating a sample or preparing a sample to be separated. However, theangle is not limited to 45 degrees. At an angle smaller than 90 degrees,an affect of the invention can be obtained. When the FIB optical axis istilted from the surface of a sample by an angle less than 30 degrees, aprocess area for separating a micro sample is enlarged and the samplesurface is wasted. When the angle becomes 75 degrees or more, the anglefrom the surface of an actually processed wall face becomes nearly 90degrees and the process depth for separating the micro sample increases.There are cases such that the process time becomes longer and, further,the micro sample cannot be separated. In order to separate a microsample, therefore, the angle formed between the sample irradiation axisof a beam and the surface of the sample is preferably in a range from 30degrees to 75 degrees.

Although the designing of the apparatus is simplified by setting theangle formed between an almost mechanical center axis of the objectivelens in the focused ion beam irradiating system and the surface of thespecimen base to 45 degrees so that the angle formed between the FIBoptical axis and the surface of the sample becomes 45 degrees, even whenthe angle other than 45 degrees is set, the FIB optical axis can betilted by 45 degrees from the sample surface by tilting the ion beam.

In the embodiment, a semiconductor wafer having a flat shape is used asan example of the sample. The invention is valid for, not necessarily aflat sample, but a sample of an arbitrary shape. In the above, the angleformed between the surface of a sample and the ion beam sampleirradiation axis has been described. In the case of a sample of anarbitrary shape, it is sufficient to fix an angle with a face on which asample is to be placed of the specimen stage to prepare a sample. Forexample, the invention can be also applied to what is called micromachining for separating a micro part from a sample in accordance withthe invention and connecting the separated micro part with another micropart to thereby fabricate a fine mechanical structure, a fine device, orthe like.

The sample fabricating apparatus suitable for carrying out the examplehas a structure in which an angle formed between an almost center axisof a mechanical column including a focused ion beam irradiating opticalsystem and the face on which a sample is placed of the specimen stage isfixed and is characterized by including means for separating a requestedportion in a sample and a probe for supporting the separated sample. Ina semiconductor wafer having a flat shape as a sample, the sampleplacement face and the surface of a sample are parallel to each other.Obviously, the angle formed between the sample irradiation axis of thefocused ion beam and the sample surface and the angle formed between thesample irradiation axis of the focused ion beam and the sample placementface of the specimen stage are the same.

In the embodiment, the sample is scanned with a focused ion beam. Atthis time, the angle of a focused ion beam incident on the sampleslightly varies depending on the scan position, but the change in theincident angle of an ion beam in association with such scanning is notincluded in a change in the angle between the sample irradiation axis ofthe focused ion beam and the surface of the sample. That is, when thesample is scanned with the focused ion beam, it is assumed that theangle formed between the sample irradiation axis of the focused ion beamand the surface of the sample can be fixed. The sample irradiation axisof the focused ion beam denotes a center line of an ion beam incident onthe surface of a sample when the scanning is stopped and there is nodeflection by a scan electrode.

Second Embodiment

Another sample fabricating method as an embodiment of the invention willnow be described by referring to FIGS. 6( a) to 6(d) A samplefabricating apparatus similar to the apparatus shown in FIG. 4 is used.

First, a mark indicative of the fabrication position of a membrane forTEM observation and a protection film are formed on a specimen base. Arectangle whose one side is in the direction of projection of theirradiation axis of an FIB to the base surface onto the surface of thesample is scanned with the FIB 1 on the specimen base to form tworectangular holes 301 (FIG. 6( a)) having a depth of about 15 .mu.m andtapered in the depth direction. In this case, a membrane between the tworectangular holes 301 is a sample as a target and the thickness of themembrane is about 100 nm. Subsequently, membrane both ends 302 are cut.By using the axis perpendicular to the surface of the sample as arotation axis, the sample is turned by about 90 degrees. By performingan image process on a secondary electron image formed by secondaryelectrons generated from the sample irradiated with the FIB 1, the tworectangular holes 301 formed so far are recognized. The FIB irradiationposition is controlled by the FIB controller 65 on the basis of thesample shape information, the bottom of a sample membrane 303 is cutwith the FIB 1 as shown in FIG. 6( c) to thereby separate the samplemembrane 303 from the specimen base. Alternately, the sample membrane303 is not separated and the process is finished while leaving aresidual area which can be broken by a little impact as a preparationfor separation in a post process. After that, the specimen base is takenout from the sample fabricating apparatus and, by using staticelectricity of a glass stick 304 in atmosphere, the sample membrane 303is moved from the specimen base onto a TEM sample holder. When thesample membrane 303 as a micro sample is not completely separated, animpact is given to the micro sample residual area by the glass stick304, the sample membrane 303 is separated from the specimen base. Afterthat, by similarly using the static electricity of the glass stick 304,the sample membrane 303 is moved from the specimen base onto the TEMsample holder. The method and apparatus for specimen fabrication forprocessing most of the outer shape of a micro sample with an ion beamwithout taking out the sample membrane 303 as a micro sample in theapparatus are also included in the invention.

Although at least one of both sides of the sample membrane is cut inFIG. 6( b) before the sample is turned by about 90 degrees in themethod, it may be cut after the turn. The order of fabrication of thetwo rectangular holes, cutting of both sides of the sample membrane,cutting of the bottom of the sample membrane, and the like is notlimited.

Although image processing is used in the embodiment, in a manner similarto the first embodiment, the operator of the apparatus may observe asecondary electron image and control an FIB irradiation position.

In the foregoing embodiment, in the series of processes of separating asample from a specimen base or preparing the sample to be separated, theangle formed between the FIB and the surface of a sample is 45 degreesand is unchanged. That is, the process of tilting the stage is notincluded. According to the embodiment, therefore, even if the functionof tilting the specimen stage is eliminated to reduce the size of thewhole apparatus, preparation of a sample for analyzing, observing, ormeasuring a micro area by separating a micro sample from the sample orpreparing the micro sample to be separated can be realized. Also in thecase of an apparatus in which the specimen stage has the tiltingfunction in a manner different from the embodiment, the time required totilt the stage is unnecessary and the sample fabrication time is maderelatively short. A problem such that the surface of a sample cannot beobserved before and after the specimen stage is tilted is also reduced.In the embodiment, a micro sample exists in the specimen base at thetime of preparing a membrane for the TEM sample, so that the precisionof the section processing position is relatively lower as compared withthe first embodiment. However, the processes of operating the probe,forming an ion beam assist deposition film for adhering a probe and amicro sample, and the like are not included, so that the samplepreparation time can be shortened.

In a manner similar to the first embodiment, the FIB irradiation angleis not always limited to 45 degrees. When the angle is smaller than 90degrees, the effects of the invention can be obtained.

Third Embodiment

FIG. 7 is a schematic configuration diagram of a sample fabricatingapparatus having an electron beam irradiating apparatus as an embodimentof the invention. A sample fabricating apparatus 17 has a vacuum chamber41 in which an ion beam irradiating optical system 35, a secondaryelectron detector 36, a deposition-gas supplying source 37, a probe 3, aspecimen stage 39, and the like are disposed in a manner similar to thesample fabricating apparatus of the second embodiment. Similarly, theion beam irradiating optical system 35 is mounted relative to the stage39 so that the angle formed between the FIB optical axis and the surfaceof the sample becomes 45 degrees. The specimen stage has the function ofturning around a line segment perpendicular to the surface of a sampleas a rotation axis. In the apparatus, an electron beam irradiatingsystem constructed by a field emission electron gun 81 for emitting anelectron beam, an electron beam lens 82, an electron scanning electrode83, and the like is mounted. As apparatuses for controlling theapparatus, not only a stage controller 61, a manipulator driver 62, anamplifier 63 for the secondary electron detector, a deposition gascontroller 64, and an FIB controller 65 but also an electron guncontroller 91, an electron beam irradiating optical system controller92, an electron beam scanning controller 93, a central processing unit74, and the like are disposed. The central processing unit 74 has thefunction of recognizing the shape of a sample by performing an imageprocess on a secondary electron image formed by secondary electronsgenerated from the sample irradiated with the FIB or an electron beam84. The central processing unit 74 also has the function of irradiatinga desired position of the sample shape with the FIB 1 by the FIBcontroller 65 on the basis of sample shape information and the functionof irradiating a desired position of the sample shape with the electronbeam 84 by the electron gun controller 91.

The operation of the ion beam irradiating optical system 35 is similarto that of the second embodiment. An operation of emitting an electronbeam will now be described. An electron source of the electron beamirradiating apparatus is a field emission electron gun 81 and anarbitrary position in the specimen base 38 can be aimed by an electronscanning electrode 83. A process area 42 irradiated with an FIB can bealso scanned and irradiated with the electron beam 84. For theoperation, preparation is made as follows. First, the FIB 1 is condensedto a spot and emitted to a sample. The irradiation trace in the spotshape is scanned with the electron beam 84, secondary electrons aredetected, and the spot-shaped irradiation trace is observed, therebyclarifying the relation between the irradiation position of the FIB 1and the electron beam irradiation position. The relation is stored inthe central processing unit 74. Therefore, on the basis of the storedinformation, the process position of the FIB 1 can be automaticallyirradiated with an electron beam, and the process status can beobserved. All the above-described controls are performed by the centralprocessing unit 74.

The sample fabricating method is similar to each of the methodsdescribed in the first and second embodiments. In the first and secondembodiments, the image process on a secondary electron image formed bysecondary electrons generated from a sample irradiated with an FIB isused for controlling the irradiation position of the FIB. However, inthe apparatus of the third embodiment, a secondary electron image formedby secondary electrons generated from a sample irradiated with anelectron beam can be used. When the sample irradiated with an electronbeam is observed, as compared with preparation of a sample only withirradiation of the FIB, the number of damages in the surface of a sampleis much smaller, and the sample preparation in shorter time can berealized.

According to the third embodiment, in a manner similar to the first andsecond embodiments, obviously, the sample fabricating apparatus forfabricating a sample for analyzing, observing, or measuring a micro areaby separating a micro sample from a sample or preparing the micro sampleto be separated, which is suitable from the viewpoint that the operationof the apparatus can be automated and the burden on the operator can belessened is provided.

Fourth Embodiment

A schematic configuration diagram of a sample fabricating apparatus asan embodiment of the invention will be described by referring to FIGS.10( a) and 10(b).

In the fourth embodiment, a focused ion beam tilting function capable ofchanging a focused ion beam incident direction by at least 15 degrees isrealized by a mechanism of varying a tilt angle with respect to aspecimen stage of a mechanical column including the focused ion beamirradiating system.

A sample fabricating apparatus 17 has a vacuum chamber 41 in which anion beam irradiating optical system 35 constructed by an ion source 32,a beam limiting aperture 33, an ion beam scanning electrode 34, an ionbeam lens 31, and the like; a secondary electron detector 36 fordetecting secondary electrons and secondary ions emitted from a sampleirradiated with the FIB; a deposition-gas supplying source 37 forsupplying an original material gas to form a deposition film in an ionbeam irradiation area; a probe 3 attached at the tip of a manipulator42; a specimen stage 39 on which a specimen base 38 such as asemiconductor wafer or a semiconductor chip is placed; a sample holder40 for fixing a micro sample as a part extracted from the specimen base38, and the like are disposed. The ion beam irradiating optical system35 is constructed so as to set the angle of the FIB irradiation axistilted from the specimen base surface in a range from 75 degrees to 90degrees. In the embodiment, the ion beam irradiating optical system 35and the vacuum chamber 41 are connected to each other via a bellows 45,and deformation of the bellows is used. FIG. 10( a) shows a state wherethe angle of the FIB irradiation axis from the surface of the specimenbase is 90 degrees, and FIG. 10( b) shows a state where the angle is 75degrees. As apparatuses for controlling the apparatus, a stagecontroller 61 mainly including an electric circuit and an arithmeticunit, a manipulator driver 62, an amplifier 63 for the secondaryelectron detector, a deposition gas controller 64, an FIB controller 65,a central processing unit 74, and the like are disposed.

FIGS. 12( a) to 12(d) show a sample fabricating method according to thefourth embodiment. Conventionally, the tapered trench 408 is formed bytilting the specimen stage and obliquely irradiating the surface of asample with the FIB 1. In place of tilting the specimen stage, it issufficient to tilt the ion beam irradiating optical system 35 as shownin FIG. 10( b) and form the tapered trench 408 as shown in FIG. 12( c).The other processes are similar to those in the conventional technique.

According to the embodiment, the sample fabricating apparatus capable offabricating a sample for analyzing, observing, or measuring a micro areaby separating a micro sample including a requested specific area from asample of an electronic part such as a semiconductor wafer, asemiconductor device, or the like and preparing the micro sample to beseparated without tilting the specimen stage is realized by a focusedion beam tilting function capable of changing a focused ion beamincident direction by at least 15 degrees. In particular, according tothe embodiment, since the focused ion beam incident angle can beselected in preparation of a sample, various sample fabricating methodsand sample shapes can be realized.

Fifth Embodiment

A schematic configuration of a sample fabricating apparatus as anembodiment of the invention will now be described by referring to FIG.11. In the fifth embodiment, a focused ion beam deflecting functioncapable of changing a focused ion beam incident direction at least by 15degrees is realized by electric deflection.

A sample fabricating apparatus 17 has a vacuum chamber 41 in which anion beam irradiating optical system 35, a secondary electron detector36, a deposition-gas supplying source 37, a probe 3, a specimen stage39, a sample holder 40, and the like are disposed in a manner similar tothe third embodiment. In this case, a deflector 51 for changing angle isfurther disposed between the objective lens 44 and the specimen stage39. By an ion beam deflecting action of the deflector 51, the angle ofthe FIB optical axis with respect to the specimen base surface can beset so as to be changed in a range from 75 degrees to 90 degrees. Asapparatuses for controlling the apparatus, a stage controller 61 mainlyincluding an electric circuit and an arithmetic unit, a manipulatordriver 62, an amplifier 63 for the secondary electron detector, adeposition gas controller 64, an FIB controller 65, a central processingunit 74, and the like are disposed.

The sample fabricating method according to the fifth embodiment is shownin FIGS. 12( a) to 12(d). Conventionally, the tapered trench 408 isformed by tilting the specimen stage to obliquely irradiate the surfaceof a sample with the FIB 1. In place of tilting the specimen stage, itis sufficient to tilt the ion beam irradiation axis relative to thesample as shown in FIG. 11 by the deflector 51 for changing angle andform the tapered trench 408 as shown in FIG. 12( c). The other processesare similar to those in the conventional technique.

According to the fifth embodiment, the sample fabricating apparatuscapable of fabricating a sample for analyzing, observing, or measuring amicro area by separating a micro sample including a requested specificarea from a sample of an electronic part such as a semiconductor wafer,a device, or the like or preparing the micro sample to be separated isrealized by an electric deflecting action of the deflector for changingangle capable of changing a focused ion beam incident direction by atleast 15 degrees. In particular, the mechanical apparatus configurationis simplified, the apparatus manufacturing cost can be reduced and,further, the focused ion beam incident angle can be selected inpreparation of a sample. Thus, various sample fabricating methods andsample shapes can be realized.

Sixth Embodiment

FIG. 13 is a configuration block diagram showing an embodiment of asample fabricating apparatus according to the invention.

The sample fabricating apparatus has: a specimen stand 1002 which ismovable but is not tilted on which a sample 1 such as a semiconductorwafer or a semiconductor chip is placed; a specimen-stage positioncontroller 1003 for controlling the position of the specimen stand 1002to specify the position of observing and processing the sample 1001; anion-beam irradiating optical system 1005 for irradiating a peripheralportion of the observation position of the sample 1001 with an ion beam1004 to form a hole for observation; an electron-beam irradiatingoptical system 1007 for emitting an electron beam 1006 for observing theperipheral portion of the sample 1001; and a secondary-electron detector1008 for detecting secondary particles (for example, secondaryelectrons) from the sample 1001.

The configuration of the ion-beam irradiating optical system 1005 is asfollows. An acceleration voltage with respect to the ground potential isapplied to an ion source 1009 for generating ions by a power source 1010for acceleration voltage. When emission of ions of the ion source 1009is unstable, Joule's heating is performed by a power source 1011 forJoule's heating to improve the state of the ion source 1009. In anextractor 1012 for generating an ion extracting electric field, anextraction voltage is applied from an extractor power source 1013 to theion source 1009. Flare of the extracted ion beam is limited by anaperture 1014. The aperture 1014 has the same potential as that of theextractor 1012. An ion beam passed through the aperture 1014 iscondensed by a condenser lens 1016 to which a condensing voltage isapplied by a condenser-lens power source 1015.

The condensed ion beam scans while being deflected by a deflector 1018to which a deflector power source 1017 is applied. The deflector powersource 1017 is constructed by power sources 1019 and 1020 for deflectionin the X direction and power sources 1021 and 1022 for deflection in theY direction. Potentials Vx/2 and Vx/2 of the same absolute value andopposite polarities are applied to counter electrodes in the X directionin the power sources 1019 and 1020. Potentials Vy/2 and Vy/2 aresimilarly set in the Y direction for the power sources 1021 and 1022.The deflected ion beam is condensed onto the surface of the sample 1001by an objective lens 1024 to which an objective voltage is applied froman objective-lens power source 1023.

The power source 1010 for acceleration voltage, extractor 1013,condenser-lens power source 1015, deflector power source 1017, andobjective-lens power source 1023 are controlled by a controller 1025 forion-beam irradiating optical system. The optical axis of the ion beam ofthe ion-beam irradiating optical system 1005 is tilted relative to thesurface of the sample 1.

The electron-beam irradiating optical system 1007 is constructed by anelectron source 1026 for generating electrons, a deflector 1027 fordeflecting and scanning an electron beam, and the like.

The controller 1025 for ion-beam irradiating optical system,specimen-stage position controller 1003, a controller 1028 forelectron-beam irradiating optical system for controlling theelectron-beam irradiating optical system 1007, a monitor 1029 fordisplaying information detected by the secondary-electron detector 1008,and the like are controlled by a central processing unit 1030. Thespecimen stage 1002, ion-beam irradiating optical system 1005,electron-beam irradiating optical system 1007, secondary-electrondetector 1008, and the like are disposed in a vacuum chamber 1031.

FIG. 14 shows an example of processing a sample in the ion-beamirradiating optical system tilted for observing a section. In theconfiguration, an ion-beam irradiating optical axis 1035 is tilted froman axis 1040 perpendicular to the surface of the sample 1001. A tiltangle 1041 is set to an angle θ larger than 0° and smaller than 90°.1036 denotes an optical-axis projected line which is the ion-beamirradiating optical axis 1035 projected on the surface of the sample. Aprocessed hole 1039 is formed here to observe a formed section 1038. Itis now assumed that a requested-section edge 1037 as a cross line of theformed section 1038 and the sample surface is parallel to theoptical-axis projected line 1036 as shown in FIG. 14.

At this time, the ion beam process setting is made by, as shown in FIG.15, setting an ion-beam scan area 1046 on a secondary electron image1045 in the monitor 1029. In this case, the requested-section edge 1037is parallel to the optical-axis projected line 1036 (imaginary linewhich does not exist on the secondary electron image).

FIG. 16 shows a sample processed section in this case. In this case, theion beam 1004 is emitted in parallel with a requested section 1052 toform the processed hole 1039. If ideal processing is realized, theformed section coincides with the requested section 1052. However, inreality, there are an influence of the ion beam flare, re-deposition,and the like, a section 1052 having a process taper angle at is formed.Consequently, a positional deviation occurs with the distance in thedepth direction, and there is the possibility that the accurate sectioncannot be observed, so that the following improvement is necessary.

As shown in FIG. 17, when an ion beam 1055 is emitted while being tiltedonly by a tilt angle corresponding to the taper angle to form aprocessed hole 1054, a section 1056 is formed accurately in the positionof the requested section 1052. In other words, it is sufficient toadjust the set section depression angle αd of a set section 1058 so asto coincide with the tilt angle αt corresponding to the taper angle inFIG. 16.

In order to realize the tilting by the not-tilting specimen stage,process setting shown in FIGS. 18( a) and 18(b) is made. In FIG. 18( a),setting is made so that a deflection scan area end 1061 (which is aset-section edge) of an ion-beam scan area 1062 forms a rotation angle1063 for fabrication (in this case, expressed as Φd) with respect to theoptical-axis projected line 1036. As shown in FIG. 18( b), it is alsopossible to turn the whole secondary electron image 1045 by Φd anddisplay the turned image. In this case, the imaginary optical-axisprojected line 1036 is turned by Φd. An ion-beam scan area 1066 and adeflection scan area end (which is a set-section edge) 1065 are seen tobe perpendicular on the secondary electron image 1045 in a mannersimilar to FIG. 15. Consequently, it is easier for the operator to makethe fabrication setting. Φd is calculated by the controller 1025 forion-beam irradiating operation system by Formula 1 to therebyautomatically set the scan of the deflector 1018.1d=arctan(tan d(sin)2−(tan d.times. cos)2)  Formula 1

Since the ion beam optical axis tilt angle θ is determined in theapparatus, the rotation angle φd of fabrication setting with respect tothe set section depression angle ad is unconditionally determined. Inthis case, −θ.ltoreq.αd.ltoreq.+θ is satisfied.

FIG. 19 shows the process at this time. A set-section edge 1071 of aprocessed hole 1072 is deviated from the optical-axis projected line1036 by an angle 1074 (expressed as a rotation angle βd of set-sectionedge). βd is expressed by Formula 2.2d=arcsin(tan d tan)  Formula 2

The relation between βd and Φd is simply expressed as Formula 3.βd=arctan(cos θ.times. tan Φd)  Formula 3

That is, as shown in FIG. 20( a), in FIG. 15 showing the secondaryelectron image in the case where the process rotation angle Φd is 0°,when the state where a direction 1081 of the section processed structureis parallel to the optical-axis projected line 1036 is a turn reference(0° in this case) of the specimen stage 3, as shown in FIG. 20B, whenthe specimen stage is turned by βd, the set-section edge 1071 coincideswith the direction 1081 of section processed structure, and a requestedobservation section can be prepared.

As described above, since the process rotation angle Φd is determined bythe set-section depression angle αd, the specimen stage rotation angleβr determined from the rotation angle βd of the set-section edge is alsounconditionally determined with respect to the set-section depressionangle ad. Consequently, by calculating Formula 2 by a sample positioncontroller 1018, turning of the specimen stage in the direction of thestructure from which a section is extracted can be automaticallycontrolled.

The flow of the above setting operations is expressed by a flow chartshown in FIG. 21. First, the depression angle αd of the set section isinput by the user (1091). For example, as shown in FIG. 22A, byinputting the depression angle αd of the set section to a set area 1101for set-section depression-angle on a monitor 1029, it is transmitted toa controller 1025 for ion-beam irradiating optical system via thecentral processing unit 1030.

Subsequently, the user sets a requested-section edge (1093). Forexample, as shown in FIG. 22( a), the requested-section edge is set bydesignating a start point (Xs, Ys) 1103 and an end point (Xe, Ye) 1104of the requested-section edge 1102 on the secondary electron image 45.The target position can be also set from CAD (Computer-Aided Design)data of device designing. In this case, a lower layer wiring positionwhich is not in the top surface of a sample can be also set. In the CADdata, in the step of setting the requested-section edge (1093), thestart point (Xs, Ys) 1103 and the end point (Xe, Ye) 1104 of therequired-section edge 1102 can be also numerically set as coordinateinformation. The arrow 1105 in FIG. 22( a) expresses therequested-section edge normal direction. In the direction of the arrow,an ion beam processed hole is formed.

On the basis of the above information, first, an ion beam scan range isdetermined. A case of tilting the ion beam scan itself for capturing asecondary electron image as described by referring to FIG. 18( b) willbe described. First, the rotation angle Φd for fabrication is calculatedby Formula 1 (1092). By scanning an ion beam while being deflected bythe rotation angle Φd for fabrication, deflection coordinates (Xi, Yj)before the scanning the ion beam are converted to (Xij, Yij) expressedby Formulae 4 and 5.Xij=Xi cos Φd+Yj sin Φd  Formula 4Yij=−Xi sin Φd+Yj cos Φd  Formula 5

(i=1 to n, j=1 to m) for defining the ion beam scan area are determinedfrom the requested-section edge (Xs, Ys) and (Xe, Ye) and arequested-section depth Zd (1095). For example, as shown in FIG. 22A,the requested-section depth Zd set in 1094 is input to a set area 1106for the requested-section depth on the monitor 1029 and is therebytransmitted via the central processing unit 1030 to the controller 1025for ion-beam irradiating optical system. (i=1 ton, j=1 to m) aredetermined from the length of the processed hole determined from thelength of the requested-section edge and the width of the processed holedetermined from the section observation angle and the requested-sectiondepth Zd. Deflector voltages corresponding to (Xij, Yij) are calculatedby Formulae 6 and 7 (1096).Vxij=kx.times.Xij  Formula 6Vyij=ky.times.Yij  Formula 7

where kx and ky are coefficients of deflection in the X and Ydirections, respectively, and are determined in the apparatus on thebasis of the power source 1010 for acceleration voltage, the length ofthe deflector 1018, distance between the counter electrodes, distancebetween the deflector 1018 and the sample 1001, and the like. Thevoltage (Vxij, Vyij) is applied from the deflector power source 1017 tocontrol the voltage of the deflector 1018. At this time, as shown by1065 in FIG. 18( b), the set-section edge becomes perpendicular on thesecondary electron image 1036. The specimen stage rotation angle βrnecessary to make the requested-section edge 1102 coincide with theset-section edge 1065 by the turning of the specimen stage 1002 iscalculated by the specimen-stage position controller 1003 by Formula 8,and the specimen stage 2 is turned.βr=arctan(cos θ×Φd)−arctan(cos θ×X _(s) −X _(e) over Y _(s) −Y_(e))  Formula 8

At this time, on the secondary electron image 1045, as shown in FIG. 22(b), an ion-beam scanning area 1108 is set as an area surrounded by (X11,Y11) 1109, (X1 m, Y1 m) 1110, (Xn1, Yn1) 1111, and (Xnm, Ynm) 1112 withrespect to a requested-section edge 1107. By scanning the area with anion beam so as to be processed, a requested section is formed.

If there is a process error due to flare of the ion beam and it is aproblem, the deflection scan area end formed by a line segmentconnecting the (X11, Y11) 1109 and (X1 m, Y1 m) 1110 is moved to theright direction only by an amount of the error from the requestedsection 1107 in FIG. 22( b) and is set. In such a manner, the formedsection becomes the requested section 1107.

An actual process example in the case where the ion beam optical axistilt angle θ is 45° will now be described. Table 1 shows set values (indegrees, calculated to one digit to the right of the decimal) of theprocess rotation angle Φd and the rotation angle βd of the set-sectionedge with respect to the depression angle αd of the set section rangingfrom −45° to +45° by calculating Formulae 1 and 2.

1TABLE 1 Rotation angle Set-section Process of the depression anglerotation angle set-section edge αd (degree) Φd (degree) βd (degree) −45−90 −90 −40 −65.4 −57.0 −30 −45 −35.3 −20 −28.9 −21.3 −10 −14.2 −10.2 00 0 10 14.2 10.2 20 28.9 21.3 30 45 35.3 40 65.4 57.0 45 90 90

FIG. 26 shows the relation between the depression angle of the actuallyformed section and the depression angle ad of the set section when theprocess is performed under those conditions. If the process is ideallyperformed, an experimental value 1141 is supposed to coincide with anideal line 1142, but they do not coincide with each other in reality.The deviation is caused by a taper formed in the process. In order toform an accurate requested section, therefore, the following flow forautomatically correcting the taper angle at is necessary.

The taper angle αt depends on not only ion beam energy, a samplematerial, and the like, but also the optical axis tilt angle θ of theion beam and the requested-section depression angle αe. Consequently,when the taper angle is expressed as αt (αe, θ), by using theset-section depression angle ad expressed by the following Formula 9 todeflect Φd of Formula 1 and controlling βr in Formula 8 by turning thespecimen stage, the formed section and the requested section can be madecoincide with each other.αd=αe+αi(αe,θ)  Formula 9

That is, by employing a table using αe and θ in the taper angle αt (αe,θ) as parameters, the section can be automatically formed in therequested section position. When θ is 45°, the table is as shown inTable 2.

2 TABLE 2 Requested-section depression Taper angle αe (degree) αt(degree) −45 3.4 −40 3.8 −30 4.6 −20 5.4 −10 6.2 0 7.0 10 7.7 20 8.5 309.3 40 10.1 45 10.5

As described above, with the configuration of the invention, byautomatically controlling the rotation angle Φd of process setting andthe rotation angle βr of the specimen stage, the tilt irradiation angleαd of an ion beam can be arbitrarily selected, and taper eliminatingprocess or the like is also facilitated.

Seventh Embodiment

In a seventh embodiment, an example where a shape to be actuallyprocessed for forming a section is a rectangle will be described.

Since the ion beam scanning area described in the sixth embodiment has arectangular shape as shown in FIG. 18( a), the shape actually processedon the sample surface is a parallelogram as shown by 1151 in FIG. 27(a). Reference numerals 1153, 1154, and 1155 are metal lines of a deviceand an object is to process the positions of the metal lines 1153 and1154. A formed-section edge 1152 is processed so as to crossperpendicular to the metal lines 1153 and 1154. In this case, aprocessed edge 1156 other than the formed section edges is formedobliquely with respect to the formed-section edge 1152 and there is acase such that the metal line 1155 which is inherently unnecessary to beprocessed is also processed.

Consequently, in some cases, a process as shown in FIG. 27( b) isdesired. Specifically, the processed shape on the sample surface is setto a rectangle as shown by 1157, and a processed edge 1159 other than aformed-section edge 1158 is made parallel to the metal line 1153 and thelike, thereby enabling only the target metal lines 1153 and 1154 to beprocessed.

In order to realize the process, it is sufficient to make processsetting shown in FIG. 28. FIG. 28 corresponds to FIG. 18( b) and showsthat the whole secondary electron image 1161 is turned by Φd. In thiscase, although a scanning-area edge 1163 is set in a manner similar tothe set-section edge 1065 in FIG. 18( b), a scanning area 1162 is set ina parallelogram different from the rectangular-shaped scanning area1066. An interior angle γ (shown in degrees) of the parallelogramindicated by 1164 is expressed by Formula 10.γ=90−Φd+arctan {(cos θ)²×tan Φd}  Formula 10

As described above, by performing a process by setting the scanning area1162 in the parallelogram shape, the rectangular process of FIG. 27( b)can be realized, so that an arbitrary tilt process can be realizedwithout processing an unnecessary area.

Eighth Embodiment

In an eighth embodiment, an example of applying the sample fabricatingapparatus according to the invention to a membrane sample for TEMobservation, energy dispersive X-ray spectrometry (EDX), or electronenergy loss spectroscopy (EELS) will be described.

The membrane for TEM observation is requested to be thin in order toimprove observation resolution and is usually processed to a thicknessof about 100 nm. However, in the case of irradiating an observationsection with an ion beam in parallel as described in the sixthembodiment, when the TEM membrane is processed, tapered membranesections 1115 and 1116 as shown in FIG. 23 are formed. Consequently, asample has a thickness distribution in the depth direction with respectto a requested observation section 1117. In this case, an extrastructure is also included in a deep area, so that the observationaccuracy deteriorates. Further, in the case of using the EDX or EELS foranalyzing a composition element, quantitativeness of the signal amountof an X-ray and an electron beam is important. In the case of a sampleof which film thickness varies as shown in FIG. 23, the quantitativeanalysis of compositions cannot be carried out.

In order to solve the problem, as described in the sixth embodiment, therotation angle Φd of processing setting of an ion beam is controlled bythe controller 1025 for ion-beam irradiating optical system, and therequested observation section 1117 is obliquely irradiated with an ionbeam 1121, thereby enabling a membrane section 1122 to be formed inparallel with the requested observation section 1117, as shown in FIG.24( a). Similarly, by setting the rotation angle βd of process settingof the ion beam in the opposite direction, a tilted ion beam 1124 shownin FIG. 24( b) can be emitted, so that a membrane section 1125 can beformed. Thus, an observation membrane having high uniformity in filmthickness can be formed.

As described above, with the configuration of the embodiment, byautomatically controlling the rotation angle Φd of process setting andthe rotation angle βr of the specimen stage, the tilt irradiation angleαd of an ion beam can be arbitrarily selected, and a membrane havinghigh thickness uniformity can be formed. Thus, the embodiment iseffective at improving the observation accuracy of the TEM observationand making quantitative analysis of EDX or EELS.

Ninth Embodiment

In a ninth embodiment, an example of applying the sample fabricatingapparatus according to the invention to a sample for analyzing thecomposition in the depth direction of Auger electron spectroscopy (AES)or secondary ion mass spectroscopy (SIMS) will be described.

In the case of analyzing a composition in the depth direction of asample portion in which the composition is uniform in the directionparallel to the surface of the sample by AES or SIMS, by analyzing asection formed at a small angle to improve the resolution in the depthdirection, the depth resolution can be improved. FIGS. 25( a) and 25(b)show a method of preparing a section suitable for such analysis.

An ion beam 1131 is emitted while being deflected by the ion beamdeflecting control described in the sixth embodiment to form a hole1133. By forming a section 1132 in such a manner, the sample internalstructure exposed in the section is wider than that in the sample depthdirection. The formed section 1132 is irradiated with an electron beam1134, Auger electrons are detected and dispersed, and an in-planecomposition distribution in the formed section 1132 is obtained, therebyobtaining a composition distribution in the depth direction of thesample 1001. The method can be also used for element analysis in thedepth direction by the SIMS by emitting an ion beam in place of theelectron beam 1134, detecting secondary ions, and performing massspectrometry.

As described above, by forming the tapered section at a small angle bythe sample fabricating apparatus, the resolution of analysis ofcomposition in the depth direction of AES, SIMS, or the like can be alsoimproved.

Although the embodiment has been described by using the process with anion beam as an example, the invention can be applied to a process using,not necessarily the ion beam, but a charged particle beam which can beprocessed.

In the sample fabricating method according to the invention, in theseries of processes for separating a micro sample from a specimen stage,the angle formed between the FIB and the sample surface is not changed,so that the process for tilting the stage is not included. In the samplefabricating method of the invention, therefore, even when the functionof tilting the specimen stage is omitted to reduce the size of the wholeapparatus, preparation of a sample for analyzing, observing, ormeasuring a micro area by separating a micro sample from a sample orpreparing the micro sample to be separated can be realized. Also in thecase of the apparatus in which the specimen stage has the tiltingfunction, time required to tilt the stage is unnecessary, so that samplefabrication time is made relatively short. The problem such that thesample surface cannot be observed before and after the specimen stage istilted can be also reduced.

According to the invention, the sample fabricating apparatus forpreparing a sample for analyzing, observing, or measuring a micro areaby separating a micro sample from a sample or preparing the micro sampleto be separated, which is suitable from the viewpoint that the operationof the apparatus can be automated and the burden on the operator can belessened is provided.

According to the invention, with the configuration of the apparatususing the not-tilted specimen stage effective at reducing the apparatusmanufacturing cost, an ion beam can be emitted at an arbitrary angle anda very accurate section can be formed, so that the precision of FIB orSEM observation can be increased. A sample membrane having uniform filmthickness can be formed, so that it is effective at improving theprecision of the TEM observation and making quantitative analysis of EDXand EELS.

1. A sample fabricating method comprising: a first step of irradiating afirst ion beam at a surface of a specimen in order to form a firsttrench relative to the surface of the specimen, the surface of thespecimen being set at a predetermined angle that is inclined relative toa right angle between the surface and an optical axis of the first ionbeam during said first step of irradiating; a step of rotating thespecimen approximately 180 degrees about a rotation axis perpendicularto the surface of the specimen after the first irradiating step whilemaintaining the specimen at the predetermined angle; and a second stepof irradiating a second ion beam at the surface of the specimen in orderto form a second trench relative to the surface of the specimen, thefirst and second trenches being formed to converge within the specimento form a bottom of a sample, the surface of the specimen being setduring the second step of irradiating at the same predetermined angle atwhich the surface of the specimen is set during the first step ofirradiating, wherein the sample is defined by a pair of side walls whichface each other as formed in the first irradiating step, the secondirradiating step or in both the first and second irradiating steps, andwherein the sample is separated from the specimen or is prepared to beseparated from the specimen.
 2. A sample fabricating method according toclaim 1, wherein irradiation of the first ion beam is conducted so as toform the predetermined angle from 30 degrees to 75 degrees between thesurface of the specimen and the optical axis of the first ion beamirradiated.
 3. A sample fabricating method according to claim 1, whereinthe sample separated from the specimen or prepared to be separated fromthe specimen is extracted by using a probe.
 4. A sample fabricatingmethod according to claim 1, wherein the specimen is a wafer.
 5. Asample fabricating method according to claim 1, wherein the first stepof irradiating the first ion beam at the surface of the specimen, thestep of rotating the specimen, and the second step of irradiating thesecond ion beam at the surface of the specimen are conducted withouttilting the specimen.
 6. A sample fabricating method comprising: a firststep of irradiating a first ion beam at a surface of a specimen, thesurface of the specimen being set at a predetermined angle that isinclined relative to a right angle between the surface and an opticalaxis of the first ion beam during said first step of irradiating; a stepof rotating the specimen approximately 180 degrees about a rotation axisperpendicular to the surface of the specimen while maintaining thespecimen at the predetermined angle; and a second step of irradiating asecond ion beam at the surface of the specimen after the step ofrotating the specimen, the surface of the specimen being set during thesecond step of irradiating at the same predetermined angle at which thesurface of the specimen is set during the first step of irradiating,wherein a first trench relative to the surface of the specimen is formedin the first irradiating step, wherein a second trench relative to thesurface of the specimen is formed and the first and second trenches areformed to converge within the specimen to form a bottom of a samplewherein the sample is defined by a pair of side walls which face eachother in the first and second trenches as formed in the firstirradiating step, the second irradiating step or in both the first andsecond irradiating steps, and wherein the sample is separated from thespecimen or is prepared to be separated from the specimen.
 7. A samplefabricating method according to claim 6, wherein irradiation of thefirst ion beam is conducted so as to form the predetermined angle from30 degrees to 75 degrees between the surface of the specimen and theoptical axis of the first ion beam irradiated.
 8. A sample fabricatingmethod according to claim 6, wherein the sample separated from thespecimen or prepared to be separated from the specimen is extracted byusing a probe.
 9. A sample fabricating method according to claim 6,wherein the specimen is a wafer.
 10. A sample fabricating methodaccording to claim 6, wherein the first step of irradiating the firstion beam at the surface of the specimen, the step of rotating thespecimen, and the second step of irradiating the second ion beam at thesurface of the specimen are conducted without tilting the specimen. 11.A sample fabricating method comprising: a first step of forming a firsttapered trench in a depth direction of a sample and a pair of side wallswhich face each other by irradiating a first ion beam at a surface ofthe specimen, the surface of the specimen being set at a predeterminedangle that is inclined relative to a right angle between the surface andan optical axis of the first ion beam during said first step ofirradiating; a step of rotating the specimen approximately 180 degreesabout a rotation axis perpendicular to the surface of the specimen whilemaintaining the specimen at the predetermined angle; a second step offorming a second tapered trench in the depth direction of the sample byirradiating a second beam ion beam from an inclined angle relative tothe surface of the specimen, the first and second trenches being formedto converge within the specimen to form a bottom of a sample, thesurface of the specimen being set during the second step of irradiatingat the same predetermined angle at which the surface of the specimen isset during the first step of irradiating; and a step of extracting thesample separated from the specimen by the first and second trenches. 12.A sample fabricating method according to claim 11, wherein theirradiation of the ion beam is conducted so as to form the predeterminedangle from 30 degrees to 75 degrees between the surface of the specimenand an optical axis of the ion beam irradiated.
 13. A sample fabricatingmethod according to claim 11, wherein a probe is used in the step ofextracting the sample.
 14. A sample fabricating method according toclaim 11, wherein the specimen is a wafer.
 15. A sample fabricatingmethod according to claim 11, wherein the first step of forming thefirst tapered trench, the step of rotating the specimen, and the secondstep of forming the second tapered trench are conducted without tiltingthe specimen.